Some consider Austropotamobius pallipes as a species complex comprised of two genetically distinct species; A. pallipes and an Italian species for which the name is being discussed. The Italian species is thought to be comprised of a number of subspecies, though this depends on the author. Both the Italian form and A. pallipes can be found in Spain, France, Italy and Switzerland. It is also suggested that there are two subspecies of A. pallipes: A. pallipes pallipes which exists in France, the British Isles, Spain, Switzerland, and Germany, and A. p. subsp. nov. which is known from Liguria in Italy and the Alpes Maritimes region of France. There still exists some debate as to whether the Italian form should be raised to species level, though recent genetic work (Grandjean et al. 2000a, Fratini et al. 2005, Bertocchi et al. 2008) would support a separate species, Austropotamobius italicus with 4 subspecies.

Justification:
The White-clawed Crayfish (Austropotamobius pallipes) has been assessed as Endangered under criterion A2ce. In the last ten years this species is suspected to have undergone a decline of somewhere between 50–80% based on presence/absence data available for England, France and Italy. The situation in these countries is thought to be similar to that of the other countries in its range for which there is no population data. These global declines are largely attributed to the introduced crayfish (e.g., Signal Crayfish and Red Swamp Crayfish) and crayfish plague Aphanomyces astaci, which are now found throughout this species entire range. This species is managed and protected by a number of international and national legislations, however these are limited in their capacity to prevent the further spread of non-native species. Population monitoring is urgently required within some of the other countries for which no data was available to determine at what rate this species is being lost from aquatic systems.

Austropotamobius pallipes has a wide distribution throughout Europe. It was previously thought that the western limit of the species range was in Portugal (though it is now thought to be Extinct there), but is now northwestern Spain. Montenegro is the easterly limit, whilst Spain and Scotland are the southerly and northerly limits respectively. Its distribution is restricted in Austria, Corsica, Germany, Lichtenstein and Montenegro (Souty-Grosset et al. 2006).

England, Wales, Ireland, France and Italy once held the greatest abundance of this species, however over the last 10-20 years this species has undergone significant declines in these countries and the greatest subpopulation is now found in Ireland which is still free from the Signal Crayfish. The status of this species has recently been reviewed by Holdich et al. (2009).

Bosnia and Herzegovina: This species was recorded as present in Livno and in Boracko Lake in the Neretva drainage in 1895 and from Gacko (Herzegovina) and Ljuta (Croatia) in 1961 (Entz 1909, Karaman 1961). These drainage systems are part of the Adriatic drainage system.

Croatia: This species is reported from several localities including: Vransko Lake (Island of Cres), near the towns of vica and Gornjit Kosinj, Zrmanja, Krupa, Centina and Krka Rivers (Grube 1864, Bruina 1907). This species has been eliminated from the main stem of the River Nereta due to intensive draining and pollution (Gottstein et al. 1999). It has been described as native to Croatia in the rivers belonging to the Adriatic Sea drainage (I. Maguire and G. Klobučar pers. comm. 2009). Some populations on the south have disappeared (the Ljuta River, Vrljika River) but due to the enthusiasm of local people, before it became extinct, some crayfish were transferred to surrounding tributaries. It has not been detected in the Krka and Zrmanja Rivers, but has been seen in some of the smaller tributaries. The main causes of disappearance are regulation of river banks and intensive agriculture (pollution) on the river banks (I. Maguire and G. Klobučar pers. comm. 2009).

Czech Republic: Groombridge (1993) reports this species within the country, however Machino says this report is a mistake (Y. Machino pers. comm. 2009).

England: There has been much debate over the origin of this species within England. This species is now considered indigenous within this country following the recent work of Holdich, Palmer and Sibley (2009) in which they found a number of records to suggest that this species has been present for at least 500 years and was certainly widespread and abundant prior to the introduction of signal crayfish and crayfish plague (Thomas and Ingle 1971, Holdich and Reeve 1991). However, since the 1970s with the introduction of the Signal Crayfish (Pacifastacus leniusculus), this species has been undergoing significant declines in its range (Sibley 2003, 2004). This species is suspected to have undergone a 95% decline within Hampshire since the 1970s (A. Hutchings pers. comm. 2009). Data collected by the Environment Agency on presence/absence in southwest England, indicates that this species has undergone a decline of 31% in 10 years (occurred in 87 Water Framework Directive subcatchments prior to 1975, but was only found in 26 of these by the end of 2008) (Sibley, Holdich and Lane 2009). Rates of decline for the South West region were determined by mapping presence/ absence in sub-catchment units, and provides greater resolution than that provided by mapping presence/ absence in 10 km² grid cells (P. Sibley pers. comm. 2009); however this estimate is likely to underestimate true decline as many once dense subpopulations are rapidly disappearing (P. Sibley pers. comm. 2009). A decline of greater than 95% is suspected for the Thames region (G. Scholey and A. Ellis pers. comm. 2009); it was once present in all the major Thames tributaries but now only eight of the 55 sub-catchments (97.9% decline over a ten year period) have any records for A. pallipes since 2004 (J. Foster pers. comm. 2009). East and West Sussex are suspected to have undergone a 100% loss of A. pallipes, although a few small populations still exist in Kent (J. Foster pers. comm. 2009). East Anglia has also undergone significant losses since the 1970s with a range contraction from 384 km of occupied river (between 1970 - 2000), to just 84 km post 2000 (M. Pugh pers. comm. 2009). The situation in Britain has recently been reviewed by Holdich et al. (2004) and Holdich and Sibley (2009).

France: This species is widespread within France and is known to occur in the majority of departments (Laurent 1988, Vigneux et al. 1993, Changeux 1996). Attempts have been made to restock waterways which have been affected by the plague. The population numbers of this species are said to be declining significantly (Vigneux et al. 1993, Vigneux 1997, Changeux et al. 2004). A survey from Poitou-Charentes indicates a decline of 40% over the period 1997–2003 (52% decline since 1995) with a decline from 137 subpopulations in 1978, to 120 in 1988, to 81 in 1995, and to 45 populations in 2003 (Bramard et al. 2006). This situation is similar to what is happening across much of France: In Jura 60% of known subpopulations have disappeared since 1989 (~37% decline over a ten year period). Numerous subpopulations have disappeared in 14 departments, with declines are occurring in 26 of the 92 departments (C. Souty-Grosset pers. comm. 2009)

Germany: This species was first discovered in Germany in 1989 where it is restricted to the south-west of the country (Holdich 2002). The population numbers are declining (H. Schulz pers. comm. 2009).

Ireland: O'Keeffe (1986) estimated a population density of approximately 37,000 adults in White Lake (32 ha). Matthews et al. (1993) estimated a population density of over one million adults in Lough Lene (430 ha); both these subpopulations have since disappeared. Reintroductions have taken place and have been successful within White Lake (Reynolds et al. 2000), however the Lough Lene subpopulation has since disappeared. Crayfish plague is suspected to have caused these declines. Matthews and Reynolds (1995) estimated populations in Blessington Reservoir, Co. Wicklow, at 500 adults per 100 m of rocky shoreline, and O'Keeffe (1986) noted dense populations in Lisheen streams nearby; stream densities were up to 6.5 per m². Outbreaks of the plague in the 1980s caused losses in two catchments. Since then, slow declines are suspected to be occurring in some parts of Ireland (J. Reynolds pers. comm. 2010).

Italy: The species is native to Italy where it is the most widespread species, except for Sicily and Sardinia (Gherardi et al. 1999). The introduction of Pacifastacus leniusculus in 1981 from Austria in the South Tyrol region of Italy, may have led to the disappearance of A. pallipes in that area (Füreder and Machino 1999a). A significant decline in the number of populations within Liguria, Piedmont, and Tuscany has also been observed (Souty-Grosset et al. 2006, Gherardi et al. 2008). In Füreder et al. (2002c), 12 populations were reported within South Tyrol; in 2003 (Füreder et al. 2004) only seven of these populations remained representing an annual change of 58%, or 99.5% over 10 years. South Tyrol is thought to be exhibiting some of the greatest declines in the abundance of this species.

Montenegro: This species is both native and introduced within this country. In the Danubian drainage it is said to be native (its presence needs to be proved), but on the Mediterranean side it is thought to be introduced (Y. Machino pers. comm. 2009).

Slovenia: Austropotamobius pallipes is native to Slovenia. This species' subpopulations are low due to the impacts of the crayfish plague (Budhina 1989, B. Sket pers. comm. 2009)

Spain: The origin of A. pallipes is uncertain. Albrecht (1983) considers that it is not native to Spain, due to a reference stating that this species was absent in 1642. Grandjean et al. (2001a) and Trontelj et al. (2005) found low genetic variability in the Spanish subpopulation, but with similarities to a subpopulation in Italy. Grandjean et al. (2001a) suggest that this could be due to anthropogenic introductions. Alternatively, this could be due to a bottleneck during the Pleistocene, and current subpopulations have arisen from a single refugium. Spanish and Italian subpopulations could be descended from an extinct intermediate population in France. However, Gutiérrez-Yurrita et al. (1999) considers A. pallipes to be indigenous to Spain. According to records, it was abundant in the 1960s, but had become scarce and restricted to northern Spain in the 1990s. Alonso et al. (2000, 2001) state that less than 1,000 small subpopulations exist in northern and north-eastern Spain. To attempt to reinstate this species, some areas are being subject to restocking. Garcia-Arberas and Rallo (2000) state that this species is still located in areas of the Basque Country where it was thought to have gone extinct

Switzerland: This species is native to Switzerland, but is currently experiencing a strong recession (D. Hefti pers. comm. 2009). It is typically found in western regions and alpine valleys, although its presence in montane lakes is thought to be as a result of introductions (Holdich 2002). It is highly sensitive to crayfish plague (Aphanomyces astaci). This species is considered as 'highly endangered' (Stucki and Zaugg 2006).

This is a freshwater species which can be found under submerged cobbles, rocks, logs, tree roots, and amongst fallen leaves in permanent water bodies such as canals, streams, rivers, lakes, reservoirs and water-filled quarries (Holdich 2003). Recently it has been found that A. pallipes can tolerate muddy habitats if tree roots or other woody habitats are available (Holdich et al. 2006). Vertical banks and overhanging vegetation have been highlighted as important features in determining crayfish abundance (Naura and Robinson 1998). It may also be found in large numbers in waters dominated by Chara sp. (Souty-Grosset et al. 2006). This species is intolerant to pollution and hydrological change. Waters containingthis species tend to be in the pH range 7-9, with calcium levels above 5 mg l-1. This species occurs in areas with relatively hard, mineral-rich waters on calcareous and rapidly weathering rocks. A study from Western France (Trouilhé et al. 2008) found the site harbouring the largest A. pallipes population had a dissolved oxygen concentration as low as 4.93 mg/L, while water temperature rose above 20°C for several consecutive days during summer. Nitrate concentrations were always found to be above 30mg/L. Principal component analyses (PCA) suggested that an increase of organic matter was a discriminant factor for the presence or absence of this species(Trouilhé et al. 2008).

It can live for more than 10 years, and usually reaches sexual maturity after three to four years. It will carry 20-160 eggs, but usually less than 100 (Holdich 2003).

Declines in this keystone species are said to negatively impact both ecosystem structure and function within freshwater environments through loss of: a) provisioning services – food production from fisheries, recreational fishing, b) regulatory and support services – trophic cascades, water purification, nutrient cycling, primary productivity, c) cultural value – recreational fishing, education, heritage. Crayfish are also an important food source to a range of species including otters, salmonids, and birds such as kingfishers (Kettunen and ten Brink 2006).

This species is affected by a range of threats, however the most widespread threat is that of the invasive alien crayfish species such as Signal Crayfish (Pacifastacus lenisculus) and Red Swamp Crayfish (Procambarus clarkii) and Crayfish Plague (Aphanomyces astaci) (Holdich et al. 2009). Invasive crayfish are aggressive predators for food and habitat, and often prey upon the White-clawed Crayfish. This species is also threatened by Thelohania contejeani or Porcelain Disease. It may be present in 10% of a population without apparent harm, but problems may occur if a higher prevalence is reached (Holdich 2003).

Significant declines are occurring across much of this species range: approximately ~52% decline over 10 years in England, ~52% decline between 1995 and 2003 within France, and a 99.5% decline estimated for a ten year period in the South Tyrol region of Italy. These countries once held the greatest abundance of this species (Thomas and Ingle 1971, Holdich and Reeve 1991). While information on the rate of decline is not available for all the countries in this species range, the situation is likely to be similar to that seen in England, France and Italy as the main threats (alien crayfish and Aphanomyces astaci) are present throughout much of this species range. The situation in Ireland is slightly less serious in that Signal Crayfish are not yet reported from here, however Aphanomyces astaci is present and already driving slow declines. This species is estimated to have undergone a 50 - 80% decline over a 10 year period over its global range. Sibley (2002) has suggested that should the current trend in the decline of this species continue, it faces possible extinction in Britain within 30 years.

It is important to note that though this species may appear to be numerous in areas, the degree of genetic variability may in fact be low. Low intra-population genetic variability has been observed in Croatia, France (Gouin et al. 2006), Italy and Spain (Bertocchi et al. 2008; Diéguez-Uribeondo et al. 2008), and Portugal. In some populations (e.g. in the basin of the River Sieve in Italy) the absence of heterozygotes and a high level of inbreeding has been observed (Bertocchi et al. 2008).

This species has been listed under the EU Habitats Directive Annex II and V and therefore requires the designation of special areas of conservation for its protection. It has also been listed under Appendix III of the Bern Convention.

In Ireland, this species is protected by the European Union (Natural Habitats) Regulations 1997. Under this regulation, Special Areas of Conservation (SACs) are designated where there are good populations of this species. This applies to all European countries.Within the United Kingdom, a Biodiversity Action Plan (UK BAP) has been developed for this species: this seeks to maintain the current distribution of the species through a combination of restricting the spread of non-native crayfish and crayfish plague, as well as providing suitable habitat features (UK Biodiversity Group 1995). Eradication of non-native crayfish in large bodies of water and rivers is difficult, if not impossible (Holdich et al.1999), although control may be achieved through trapping. Some success has, however, been achieved in enclosed waters in Scotland using natural biocides (Peay et al. 2006). It is an offence under Schedule 9 of the Wildlife and Countryside Act to keep without licence or release five of the introduced species (Pacifastacus leniusculus, Procambarus clarkii, Orconectes limosus, Astacus leptodactylus and Astacus astacus) of crayfish into the wild, a sixth (O. virilis) has yet to be added to this act (Holdich and Sibley 2009). This species is also indirectly affected by the EU Water Framework Directive which seeks to achieve good ecological status of aquatic systems. There are a number of local community education programs that aim to inform local communities on identification of native and non-native species and the legal implications of removing these species from the wild. It is also protected by the Wildlife Acts (since 1975) in Ireland. Non-native crayfish are prohibited by the Fisheries Acts within Ireland (J. Reynolds pers. comm. 2010).This species has been reintroduced (using hatchery reared individuals) into a number of sites at which it was previously found (Rogers and Watson 2007). Methodological approaches for re-introductions have been recently reviewed by Souty-Grosset and Reynolds (2009). The suitability of the target habitat, the stocking material and the stocking procedure itself are paramount during any reintroduction measure: apart from general water quality and structural parameters, a suitable habitat is ideally geographically isolated from other surface waters and human activities such as intensive fishing pressure and agricultural practices. Genetics of stocking material must be considered. However, it is first essential to make sure that the target habitat is free of crayfish plague. Analyses of experience gathered in various European countries indicate how difficult it is to get the best information as a basis for successful restocking and consequently the discussions recently conducted among European researchers and managers were aimed at achieving consensus and common strategies (Souty-Grosset and Reynolds 2009).Within Switzerland this species is regulated by the National Swiss Fisheries Legislation and is deemed 'highly endangered'. There is a closed fishing season of 40 weeks per year and minimum harvest size limit of 9 cm (Hefti and Stucki 2006).

Population monitoring within countries for which trend information is lacking, is needed. Further research within these countries, on the main drivers of decline is also required.